CN111418075A - Gamut widening display with narrow-band green phosphor - Google Patents

Abstract

The phosphor emitting green light in a narrow wavelength range can be usedThe color gamut of the display device is widened. In one aspect, a light emitting device includes a light emitting solid state device that emits blue or violet light; a first phosphor that absorbs blue or violet light emitted by the light-emitting solid-state device and in response emits green light in a spectral band having a wavelength λ_GPeak value and wavelength lambda of_{G half}The height of half the peak of the spectral band at the long wavelength edge of the band; and a second phosphor that absorbs blue or violet light emitted by the light-emitting solid-state device and emits red light in response in a spectral band having a wavelength λ_RPeak value and wavelength lambda of_{R half}The height of the peak half of the spectral band at the short wavelength edge of the band. Ratio (λ)_{R half}‑λ_{G half})/(λ_R‑λ_G) Greater than 0.70.

Description

Gamut widening display with narrow-band green phosphor

The invention was made with the support of the federal government under grant number 1534771 by the U.S. national science foundation. The federal government has certain rights in the invention. The invention also obtains rewards from the Kentucky economic development pavilion startup office according to a gift protocol KSTC-184-.

Cross Reference to Related Applications

The present application claims priority rights of U.S. provisional patent application No.62/560,539 entitled "Gamut broadening Illumination With Narrow Band Green Phosphors" (Gamut broad Illumination With Narrow Band Green Phosphors) filed on 19.9.2017, U.S. provisional patent application No.62/649,374 entitled "Gamut broadening display With Narrow Band Green Phosphors" (Gamut broad broadening With Narrow Band Green Phosphors) filed on 28.3.2018, and U.S. patent application No.15/982,193 entitled "Gamut broadening display With Narrow Band Green Phosphors" (Gamut broadening Band Green Phosphors) filed on 17.5.2018, each of which is incorporated herein by reference in its entirety.

This application also relates to U.S. patent application No.15/591,629 entitled "Phosphors With Narrow Green Emission" (Phosphors With Narrow Green Emission) filed on day 5, month 10, 2017, and U.S. patent application No.15/679,021 entitled "Phosphor-Converted White light Emitting Diodes With Narrow Band Green Phosphor" (Phosphor-Converted White L light Emitting Diodes) filed on day 8, month 16, 2017, both of which are incorporated herein by reference in their entirety.

Technical Field

The present invention relates generally to phosphors having narrow green emission and display devices including such phosphors.

Background

In a display backlight, it is desirable for the green light source to have a narrow emission wavelength, so that the light from the green light source appears more saturated, widening the green apex of the color gamut, and less loss when passing through the green filter of a typical L CD filter system, since most of its intensity is well aligned with the highest transmission of the filter.

Disclosure of Invention

The present invention relates to lighting systems that emit light having certain aspects of a Spectral Power Distribution (SPD) that can enhance the width of colors that can be rendered by a display backlight unit by widening the color gamut, or enhance the appearance of certain products by saturation of certain spectral regions in general lighting and lighting used to illuminate the products.

Drawings

Fig. 1A shows a typical transmission spectrum of a color filter set for a backlit L CD display.

Fig. 1B shows a typical transmission spectrum of another color filter set for a backlit L CD display.

Fig. 2A shows the CIE 1931x, y chromaticity diagram on which the sRGB, NTSC and Adobe RGB color gamuts are plotted.

Fig. 2B shows the CIE 1931x, y chromaticity diagram on which the sRGB, DCI-P3 and rec.2020 color gamuts are plotted.

Fig. 3A shows the CIE 1976u 'v' chromaticity diagram, on which the sRGB, NTSC and Adobe RGB gamuts are plotted.

Fig. 3B shows the CIE 1976u 'v' chromaticity diagram, on which the sRGB, DCI-P3 and rec.2020 color gamuts are plotted.

FIG. 4 shows a newly developed green phosphor material (e.g., EuAl) as described herein_1.5Ga_1.2S_4.47) Typical emission spectra of (a).

Fig. 5 shows the CIE 1976u 'v' chromaticity diagram on which the simulated color gamut of a backlight L CD display using the phosphor material of fig. 4 and standard color filters is plotted.

FIG. 6A shows a simulated emission spectrum from a conventional phosphor converted white L ED overlaid with the set of color filters in FIG. 1A.

FIG. 6B shows a simulated emission spectrum of L ED of FIG. 6A as transmitted through a color filter.

Fig. 6C shows a simulated emission spectrum of L ED of fig. 6A when transmitted through a blue filter.

Fig. 6D shows a simulated emission spectrum of L ED of fig. 6A when transmitted through a green filter.

Fig. 6E shows a simulated emission spectrum of L ED of fig. 6A when transmitted through a red filter.

FIG. 6F shows the CIE 1931x, y chromaticity diagram on which the simulated color gamut of the backlight L CD display of FIG. 6B is plotted-the sRGB and Rec.2020 color gamuts are also plotted for reference.

Fig. 6G shows a simulated emission spectrum of white L ED from another conventional phosphor conversion.

FIG. 6H shows a simulated emission spectrum of L ED of FIG. 6H as transmitted through the color filter of FIG. 1A.

Fig. 6I shows a simulated emission spectrum of white L ED from another conventional phosphor conversion.

FIG. 6J shows the emission spectrum of white L ED from conventional phosphor conversion, approximately matching that of FIG. 6I

Fig. 7A shows a simulated emission spectrum of phosphor-converted white L ED from example 1 described below.

FIG. 7B shows a simulated emission spectrum of L ED of FIG. 7A as transmitted through the color filter of FIG. 1A.

Fig. 7C shows a simulated emission spectrum of L ED of fig. 7A when transmitted through a blue filter.

FIG. 7D shows a simulated emission spectrum of L ED of FIG. 7A when transmitted through a green filter.

Fig. 7E shows a simulated emission spectrum of L ED of fig. 7A when transmitted through a red filter.

FIG. 7F shows a CIE 1931x, y chromaticity diagram on which the simulated color gamut of the backlight L CD display of FIG. 6B and the simulated color gamut of the backlight L CD display of FIG. 7B are plotted.

Fig. 8A shows a simulated emission spectrum of phosphor-converted white L ED from example 2 described below.

FIG. 8B shows a simulated emission spectrum of L ED of FIG. 8A as transmitted through the color filter of FIG. 1A.

Fig. 8C shows a CIE 1931x, y chromaticity diagram depicting the simulated color gamut of the backlight L CD display of fig. 6B, the simulated color gamut of the backlight L CD display of fig. 7B, and the simulated color gamut of the backlight L CD display of fig. 8A-8B.

Fig. 9A shows a simulated emission spectrum of phosphor-converted white L ED from example 3 described below.

FIG. 9B shows a simulated emission spectrum of L ED of FIG. 9A as transmitted through the color filter of FIG. 1A.

Fig. 9C shows a CIE 1931x, y chromaticity diagram on which the simulated color gamut of the backlight L CD display of fig. 6B, the simulated color gamut of the backlight L CD display of fig. 8B, and the simulated color gamut of the backlight L CD display of fig. 9B are plotted.

Fig. 10A shows a simulated emission spectrum of phosphor-converted white L ED from example 4 described below.

FIG. 10B shows a simulated emission spectrum of L ED of FIG. 10A as transmitted through the color filter of FIG. 1A.

Fig. 10C shows a CIE 1931x, y chromaticity diagram on which the simulated color gamut of the backlight L CD display of fig. 6B, the simulated color gamut of the backlight L CD display of fig. 9B, and the simulated color gamut of the backlight L CD display of fig. 10B are plotted.

Fig. 10D shows the emission spectrum of L ED 1 converted from the example phosphor described below, including the green phosphor from example 3 described below.

Fig. 10E shows the emission spectrum of L ED 2 converted from the example phosphor described below, including another green phosphor from example 3 described below.

Fig. 11A shows a simulated emission spectrum of phosphor-converted white L ED from example 5 described below.

FIG. 11B shows a simulated emission spectrum of L ED of FIG. 11A as transmitted through the color filter of FIG. 1A.

Fig. 11C shows a CIE 1931x, y chromaticity diagram on which the simulated color gamut of the backlight L CD display of fig. 6B, the simulated color gamut of the backlight L CD display of fig. 10B, and the simulated color gamut of the backlight L CD display of fig. 11B are plotted.

Fig. 12A shows L ED emission spectra converted by an example phosphor made from a narrow green phosphor as described in example 6 below.

FIG. 12B shows the emission spectrum of the phosphor-converted L ED of FIG. 12A when transmitted through the color filter of FIG. 1A.

Fig. 12C shows the emission spectrum of L ED of fig. 12A when transmitted through a blue filter.

Fig. 12D shows the emission spectrum of L ED of fig. 12A when transmitted through a green filter.

Fig. 12E shows the emission spectrum of L ED of fig. 12A when transmitted through a red filter.

Fig. 12F shows a simulated emission spectrum of the same phosphor blend using L ED converted with the phosphor of fig. 12A.

FIG. 12G shows a simulated emission spectrum of L ED of FIG. 12F as transmitted through the color filter of FIG. 1A.

Fig. 12H shows a CIE 1931x, y chromaticity diagram on which the simulated color gamut of the backlight L CD display of fig. 6B, the color gamut of the backlight L CD display of fig. 12B, and the simulated color gamut of the backlight L CD display of fig. 12G are plotted.

Fig. 13 shows a simulated spectrum of phosphor converted L ED including blue L ED, β -SiAlON green phosphor and red PFS phosphor, and indicates the distance between the emission peaks of the phosphors and the distance between the nearest half height of the phosphor peak.

Fig. 14 shows a simulated spectrum of phosphor-converted L ED comprising blue L ED, a narrow green phosphor with a peak wavelength of 540nm and a FWHM of 40nm, and a red PFS phosphor, and indicates the distance between the emission peaks of the phosphors and the distance between the nearest half-height of the phosphor peak.

Detailed Description

The following detailed description should be read with reference to the drawings, which depict selected embodiments and are not intended to limit the scope of the invention. The present detailed description illustrates by way of example, and not by way of limitation, the principles of the invention. This description will clearly enable one skilled in the art to make and use the invention, and describes several embodiments, adaptations, alternatives and uses of the invention, including what is presently believed to be the best mode of carrying out the invention. As used in this specification and the appended claims, the singular forms "a", "an", and "the" include plural referents unless the context clearly dictates otherwise.

The new phosphor materials with narrow-band green emission disclosed in U.S. patent application No.15/591,629 and U.S. patent application No.15/679,021 have good applicability to displays. Display manufacturers design displays according to various specifications.

For L CD based backlights, the color gamut is determined by the emission spectrum of the backlight and the transmission characteristics of the color filter set used to make the display FIGS. 1A and 1B show the transmission spectra of two typical color filter sets for a backlight L CD display, each filter set includes a red filter, a green filter, and a blue filter as shown.

As can be seen from these figures, there is significant overlap between the different color filters. This complicates enlarging the color gamut of the display because it requires the development of light sources with relatively narrow spectral peaks. Note that the relative maximum transmission of any particular color filter in the filter set can be adjusted relative to the other filters.

This overlap between the color filters is generally not significant for the blue primary color, because blue L ED, which has a narrow emission spectrum, is readily available, and the peak wavelength can be selected so that the leakage of blue L ED into the transmissive region of the green filter is negligible.

The minimum gamut and minimum requirements of most color displays are the so-called sRGB (or Rec.709) gamut. more desirable and larger gamuts are the Adobe RGB gamuts. these gamuts, as well as the NTSC gamut developed for color CRT displays are shown in FIGS. 2A and 3A below, more recently, other wider gamuts have been developed, such as the DCI-P3 gamut developed for digital cinema shown in FIGS. 2B and 3B, and the more recent gamut proposed for ultra-high definition television, which seems to be defined in part by the available technology.

When introduced for the first time around 2008 2006, L ED-based backlights for color L CD displays, the minimum target for the color gamut is the sRGB gamut, which, as can be seen in FIGS. 2A, 2B, 3A and 3B, is the minimum gamut shown, which is a difficult target to achieve because the emission band of the green phosphor available at the time is relatively wide, although it can eventually exceed the sRGB gamut, display manufacturers cannot achieve the much larger Adobe RGB gamut desired, when drawn on the CIE x, y chromaticity diagram, the sRGB gamut is only about 74% of the Adobe RGB gamut, the gamut for high quality displays is at least 90% of the Adobe gamut area.

The newly developed green phosphors disclosed in U.S. patent application No.15/591,629 and U.S. patent application No.15/679,021 may have an extremely narrow emission band in the green, which is very useful for L CD color displays and provides the ability to exceed the Adobe RGB color gamut area.

A typical emission spectrum for this type of material (phosphor in example 3 described below and in Table 2 and Table 3) is shown in FIG. 4. the relatively narrow emission band of this phosphor minimizes the overlap between the red and green primaries of a backlit L CD display, which moves the green primary away from the red primary and also increases the saturation of the green primary. the combination of these two effects greatly improves the display gamut FIG. 5 shows a simulated gamut that can be achieved using the newly developed green emitting phosphor material and standard color filters.

For general lighting applications, it is generally desirable to have the blue L ED emit at generally longer wavelengths (e.g., between 455nm and 465 nm). these blue wavelengths typically result in better color rendering indices for white light sources than the same phosphor in combination with the shorter wavelength blue L ED, and the white L ED is brighter because the blue emission is closer to photopic (photopic) maxima.

The red phosphor can be a conventional broadband red color, such as CaAlSiN₃:Eu²⁺Family (e.g., BR-102/Q or BR-101/J available from Mitsubishi Chemical) or Sr₂Si₅N₈:Eu²⁺One of them, or it may be a narrower red phosphor, such as the recently reported Sr L iAl₃N₄]:Eu²⁺Or it may be a narrow emitting quantum dot, or a manganese doped fluorosilicate family phosphor (such as PFS or KSF available from GE.) alternatively, a direct emitting red L ED, or some other red emitting source, may be used in place of the red phosphorIn terms of degree, the width of the emission, especially into longer wavelengths, does not strongly influence the color saturation of the red gamut point, because the red region of the spectrum is close to the edge of the photopic response curve, i.e. the perception of the emission by the human eye is not particularly good. The FWHM of the red phosphor still has to be considered from the point of leakage to the green gamut, and the surface brightness of the display.

Conventional backlights may utilize, for example, europium doped β -SiAlON type green phosphors (such as sold by Denka) in combination with PFS red phosphors (such as sold or licensed by GE.) the phosphors are mixed so that the color point of the L ED emission spectrum seen through the color filter will meet the white light target requirements, such as CIE x, y (0.333 ) or D65 emitters (0.313, 0.329) or another color point.

Comparative Green phosphor example

As a comparative example of a conventional phosphor-converted white L ED used in backlight applications, fig. 6A shows a simulated emission spectrum (solid line) of L ED converted using phosphors β -SiAlON, red PFS phosphor, and blue L ED having peak wavelengths of 543nm and FWHM 54nm, the simulated emission spectrum has the color coordinates CIE x, y (0.256, 0.228) — in fig. 6A, the simulated emission spectrum is overlaid by the color filter set (green filter, dashed line; blue filter, dashed line; red filter, dashed line) from fig. 1A.

FIG. 6B shows the pass filter white spectrum of L ED tuned to CIE x, y (0.333 ). fig. 6C shows the blue subpixel, fig. 6D shows the green subpixel, and fig. 6E shows the red subpixel.fig. 6F compares the simulated color gamut of a backlight L CD display using L ED to the sRGB and Rec.2020 color gamuts.2020 coverage of Rec.2020 in CIE 1931 color space is 62.3% (. an example set of color filters shown in FIG. 1A is used throughout this disclosure, although one skilled in the art will appreciate that individual color filters can be switched and relative transmission can be manipulated.)

As a second comparative example of a conventional phosphor-converted white L ED used in backlight applications, FIG. 6G shows the simulated emission spectrum of L ED converted using a green phosphor β -SiAlON with a peak wavelength of 528nm and FWHM 49nm, a red PFS phosphor, and a blue L ED with the color coordinates CIE x, y (0.249, 0.224). FIG. 6H shows the pass filter white spectrum of L ED tuned to CIE x, y (0.333 ). this corresponds to a gamut area coverage of 70.0% compared to Rec.2020 in CIE 1931(x, y) color space.

As a third comparative example of a conventional phosphor-converted white L ED used in backlighting applications, FIG. 6I shows the simulated emission spectrum of phosphor-converted L ED using the green phosphors orthosilicate phosphors, such as Isiphor RGA 524500 available from Merck KGaA, Red PFS phosphor, and blue L ED FIG. 6J shows the emission spectrum of phosphor-converted L ED made from Dow Corning (Dow Corning) OE6550, Isiphor RGA 524500 green phosphor, PFS red phosphor, and Powerto 457nm 2835 packages.

The narrow green phosphor of the present invention may include, for example, Eu (Al)_1-zGa_z)_xS_yOr Ca_1-wEu_w(Al_1-zGa_z)_xS_yA composition of form (la) wherein x is between 2.0 and 4.0 inclusive, y is between 4 and 7 inclusive, z is between 0 and 1 inclusive, and w is between 0 and 1 inclusive, but not equal to zero.

Examples of Green phosphor

Example 1 replacement of the wider β -SiAlON with the inventive phosphor having a peak emission wavelength of 540nm and a full width at half maximum of 40nm had the dual effect of extending the green color gamut point (because the green phosphor color is more saturated) and extending the red color gamut point (because the leakage of the green phosphor through the red filter is reduced) compared to the conventional backlight example just described.

One such phosphor material is Eu (Al)_1/3Ga_2/3)_2.7S_5.05Peak wavelength 541nm, FWHM 40 nm. By mixing pre-formed EuAl_2.7S_5.05And EuGa_2.7S_5.05Combined in appropriate amounts and heated to 1200 ℃ in evacuated carbon-coated tubes to produce Eu (Al)_0.33Ga_0.67)_2.7S_5.05Solid solution. EuAl_2.7S_5.05Formed by combining appropriate amounts of Eu, Al and S and heating to 1000 c in an evacuated carbon-coated tube. EuAl_2.7S_5.05Is prepared from Eu and Ga₂S₃And S and heating to 800 ℃ in an evacuated carbon-coated tube.

FIG. 7A shows a simulated emission spectrum from phosphor-converted L ED, in which green phosphor Eu (A)_l0.33Ga_0.67)_2.7S_5.05The green phosphor in the first comparative example has been replaced, the emission spectrum has the color coordinates CIEx, y (0.252, 0.223). 7B shows the pass filter white spectrum tuned to L ED for CIE x, y (0.333, 0.333.) fig. 7C shows the blue subpixel, fig. 7D shows the green subpixel, fig. 7E shows the red subpixel, fig. 7F compares the simulated color gamut of a backlight L CD display using L ED with the simulated color gamut of a comparative β -SiAlON L ED and the rec.2020 coverage in CIE 1931(x, y) color space is 68.3%. comparison of the red subpixels in fig. 6E and 7E shows that narrowing the green phosphor emission by about 15nm results in a reduction in emission intensity between 550nm and 600nm in the red subpixel.

Example 2 fig. 8A-8C show the results of blue shifting the peak wavelength of the green phosphor by 5nm to 535nm while keeping its FWHM at 40nm fig. 8A shows the simulated emission spectrum of L ED from this phosphor conversion with the color coordinates CIEx, y (0.249, 0.221) fig. 8B shows the pass filter white spectrum of L ED tuned to CIE x, y (0.333 ) fig. 8C compares the simulated color gamut of a backlight L CD display using L ED with the simulated color gamut of L ED in example 1 and the simulated color gamut of a comparison β -SiAlON L ED with 535nm peak green phosphor, the green and red color gamut points are expanded and the color gamut covers 71.0% of the color gamut of rec.2020 in CIE x, y.

One such phosphor is EuAl_1.16Ga_1.74S_5.35Peak wavelength 535nm, FWHM 42 nm. The phosphor is prepared by combining Eu and Al₂S₃And Ga₂S₃Synthesized in stoichiometric ratios to make the metal. Adding intoA small amount by weight of AlCl₃And the mixture was ground in an argon-filled glove box and sealed in a fused silica tube. The mixture was heated at 400 ℃ for one hour, and then the temperature was raised and maintained at 850 ℃ for 6 hours. The product was cooled to the chamber at a rate of about 25 c/hour.

Another such phosphor is EuAlGaS₄(disclosed in U.S. application 62/539233, filed 2017 on 31/7 and incorporated herein by reference in its entirety), peak wavelength 533nm FWHM 41 nm. By adding Eu, A1 in stoichiometric amounts under Ar₂S₃、Ga₂S₃And S are combined to synthesize the phosphor. The mixture was sealed in an evacuated quartz tube and heated to 400 ℃ (6h) and then to 800 ℃ (12 h). After grinding the product and adding 50mg of excess S, a second heat treatment was carried out, heating to 400 ℃ (6h), then to 1000 ℃ (6 h).

Example 3 FIGS. 9A-9C show the results of blue shifting the peak wavelength of the green phosphor by another 6nm to 529nm and reducing the FWHM by another 1nm to 39nm FIG. 9A shows the simulated emission spectrum of L ED from this phosphor conversion with the color coordinates CIE x, y (0.246, 0.220). FIG. 9B shows the pass filter white spectrum of L ED tuned to CIE x, y (0.333 ). FIG. 9C compares the simulated color gamut of a backlight L CD display using L ED with the simulated color gamut of L ED and the simulated color gamut of the first comparison β -SiAlON L ED in example 2. with 529nm green phosphor, the green color gamut point is expanded.

One such phosphor is EuAl_1.5Ga_1.2S_4.47Peak wavelength 529nm, FWHM 39 nm. This phosphor was prepared by mixing 0.562g of Eu powder and 0.416g of Al₂S₃、0.522g Ga₂S₃0.050g S and 0.115g AlCl₃Combined and ground in a mortar and pestle in an argon-filled glove box. The mixture is classified into4 quartz tubes sealed under the air. The tube was heated to 400 ℃ for 1 hour and then at 900 ℃ for 6 hours. The tube was then cooled to room temperature at 50 deg.C/hour.

Example 4 fig. 10A-10C show the result of blue shifting the peak wavelength of the green phosphor by another 6nm to 523nm while keeping the FWHM at 39nm fig. 10A shows the simulated emission spectrum of L ED from this phosphor conversion with the color coordinates CIE x, y (0.243, 0.222) fig. 10B shows the pass filter white spectrum of L ED tuned to CIE x, y (0.333 ) fig. 10C compares the simulated color gamut of a backlight L CD display using L ED with the simulated color gamut of L ED in example 3 and the simulated color gamut of the first comparison β -SiAlON L ED with 523nm green phosphor, further extending the green color gamut point, the effect on the red color gamut point is negligible.

One such phosphor is Ca_0.915Eu_0.085(Al_0.9Ga_0.1)₃S_5.5Peak wavelength 523nm, FWHM 39 nm. By combining CaS, EuF in stoichiometric proportions under argon₃Al metal, Ga₂S₃And S to synthesize the phosphor. The reactants were mixed using a speed mixer (SpeedMixer) and then manually ground twice using a mortar and pestle. The reactants are in Ar/H₂The mixture is heated, first at a temperature of 700 ℃ and then at a temperature of between 950 and 1100 ℃ for 1-2 hours. All temperature ramps were 10 ℃/min.

Another such phosphor is Eu (Al)_1/3Ga_2/3)_2.7S_5.05Peak wavelength 523nm, FWHM 39 nm. To synthesize the phosphor, a pre-formed EuAl is used_2.7S_5.05And EuGa_2.7S_5.05Eu (Al) in appropriate amounts in combination with a small amount of L iCl weight percent and heated to 1200 ℃ in evacuated carbon-coated tubes_0.33Ga_0.67)_2.7S_5.05Solid solution. EuAl_2.7S_5.05Is composed of Eu, Al and S in proper quantityAn empty carbon-coated tube was heated to 1000 ℃. EuAl_2.7S_5.05Is prepared from Eu and Ga₂S₃And S and heating to 800 ℃ in an evacuated carbon-coated tube.

Another such phosphor is Ca_0.5Eu_0.5Al_2.25Ga_0.75S_5.5Peak wavelength 525nm, FWHM 39 nm. The phosphor is made of pre-formed EuAl_2.5S_4.75(Eu₂O₃(1.084g, 3.08mol) and 0.415g Al powder (0.415g, 15.41mol) were combined and treated in an alumina boat in H₂Firing at 900 ℃ for 1 hour in S atmosphere), CaS, Al, Ga₂S₃And 10% CsCl flux at 950 ℃ in flow H₂And (5) synthesizing under S.

Another such phosphor is Eu_0.31Ca_0.69Al_1.03Ga_0.97S₄Peak wavelength 524nm, FWHM 41 nm. To synthesize the phosphor, Eu is added₂O₃(1.084g, 3.08mol) and 0.415g Al powder (0.415g, 15.41mol) were mixed 3 times at 2000rpm for 45 seconds using a speed mixer. Mixing the powder in an alumina boat in H₂Firing is carried out for 1 hour at 900 ℃ under the S atmosphere. The fired precursor embryos were hand ground in a glove box to break up into a powder. 3g of EuAl_2.5S_4.75Precursor, 0.2g Al powder, 0.3g CaS and 0.7g Ga₂S₃Ground manually in a mortar with a pestle. Mixing the powders in H₂Firing was carried out in an alumina cup at 960 ℃ for 2 hours under an S atmosphere.

Exemplary phosphor converted L ED 1 is encapsulated by blue L ED (3535 of Plessey), green phosphor Ca_0.5Eu_0.5Al_2.25Ga_0.75S_5.5PFS red phosphor and dow corning OE6550 silicone fig. 10D shows the emission spectrum of the L ED with CIE x, y (0.2445, 0.2678) color coordinates.

Exemplary phosphor converted L ED 2 is encapsulated by blue L ED (3535 of Plessey), green phosphor Eu_0.31Ca_0.69Al_1.03Ga_0.97S₄PFS red phosphor and Dow Corning OE6550 Silicone TreeFig. 10E shows the emission spectrum of the L ED with CIE x, y coordinates (0.2780, 0.2473).

Example 5 fig. 11A-11C show the results of blue shifting the peak wavelength of the green phosphor by another 3nm to 520nm and further narrowing the FWHM emitted to 36nm fig. 11A shows the simulated emission spectrum of L ED for this phosphor conversion with the color coordinates CIE x, y (0.241, 0.222) fig. 11B shows the pass filter white spectrum tuned to CIE x, y (0.333 ) fig. 11C compares the simulated color gamut of a backlight L CD display using L ED with the simulated color gamut of L ED and the simulated color gamut of the first comparison β -SiAlON L ED in example 4, with 520nm green phosphor, the green color gamut point is further expanded, the effect on the red color gamut point is negligible, the blue color gamut point is still slightly less saturated, which covers 75.9% of the color gamut of rec.2020 in CIE x, y.

One such phosphor is Ca_0.915Eu_0.085Al_2.7S_5.05(disclosed in US 62/539,233), peak wavelength 520nm peak with FWHM of 36 nm. The phosphor is synthesized by combining CaS, Eu, Al, and S in stoichiometric amounts. The mixture was homogenized in a mortar and pestle under argon, then charged into a carbon-coated quartz tube, which was then evacuated and sealed under vacuum. The synthesis is carried out by a stepwise heating method: 290 ℃ (17h), 770 ℃ (24h), 870 ℃ (24h) and slow cooling over 20 h. The product was recovered and manually reground before returning to a new carbon coated quartz tube and heated to 400 ℃ (6h) and 1000 ℃ (3 h).

Example 6. L EDs for backlights can also be made using broad red phosphors (such as BR-101/J sold by mitsubishi chemical) fig. 12A shows emission spectra of an example phosphor converted L0 ED made from 458nm blue L ED, a green phosphor with a peak emission wavelength 539nm and FWHM 44nm, and BR-101/J red phosphors fig. 12B shows a pass filter white spectrum tuned to CIE x, y (0.333 ) by adjusting the respective filter thicknesses fig. 12C shows a blue subpixel, fig. 12D shows a green subpixel, fig. 12E shows a red subpixel, fig. 12F shows a simulated emission spectrum of the same phosphor mixture using 450nm peak blue L ED, fig. 12C shows a blue subpixel, y (0.2540, 0.2355) fig. 12G shows a blue phosphor mixture with a color gamut coverage ratio of x, y (0.2540, 0.2355) fig. 12F shows a blue phosphor blend tuned to CIE x, y (0.333, 333) is shifted from CIE x, y (0.2540, 0.2355) to a white spectrum of a white spectrum made using a wider color gamut conversion map 18H-18% coverage ratio of a white phosphor blend made using a wider color gamut conversion CD 19H, CD 95H, 18% wider color gamut coverage ratio of a white phosphor blended with a wider color filter, comparable CIE x, CD 62, CD 95 nm, CD 62, CD 95 nm, CD 95, CD 62, CD 95, C, CD 95, CD 62, C, CD 95, C, CD 62, CD 95, CD 18, C, CD 62, CD 18.

One such phosphor is EuAl_0.92Ga_1.38S_4.45(phosphor example 5 in U.S. application 15/591,629), peak wavelength 539nm, FWHM 44 nm. The phosphor is made of Eu and Al₂S₃、Ga₂S₃And S in stoichiometric ratio with an additional 0.25 sulfur per unit of formulation and 7.5 wt% AlCl₃. The mixture was ground in an argon-filled glove box and sealed in a fused silica tube. The mixture was heated to 400 ℃ (1h) followed by 900 ℃ (6 h). The product was cooled to room temperature at 50 ℃/hour.

Tables 2, 3 and 4 below summarize the attributes of the above examples.

For example, in a first comparative example utilizing β -SiAlON and PFS, the green phosphor peak λ is_GAt about 544nm, and a red phosphor peak λ_RAt 630nm, a difference of 86nm results (upper arrow, FIG. 13). For the green peak at 575nm, the spectrum is one-half λ of its relative maximum_{G half}. Similarly, the very narrow emission of PFS is half λ of its relative maximum at a wavelength of 628nm_{R half}Result in 53nm (lower arrow, fig. 13), the ratio of the difference of the nearest half height to the difference of the full height is 0.62, the green phosphor was changed from β -SiAlON to one of the present invention having a peak wavelength of 540nm and a FWHM of 40nm, maintaining approximately the same difference of the full height, 90nm (upper arrow, fig. 14), but increasing the difference of the nearest half height to 65nm (lower arrow, fig. 14) and increasing the ratio of the difference of the nearest half height to the difference of the full height to 0.72.

For PFS phosphors, standard phosphors (such as 524nm peak orthosilicate or 540nm peak β -SiAlON) give a ratio of about 0.6, while narrower phosphors disclosed herein give ratios greater than 0.7.

If these ratios are examined in the context of energy (electron volts) rather than wavelength (nm), the general trend holds, although the ratios are about 0.03 to 0.04 lower. For example, in comparative example 1, the green phosphor peak E_GAbout 2.279eV, red peak E_RIs about 1.968eV, and has a half-height E_{G half}And E_{R half}2.157eV and 1.975eV, respectively, resulting in a ratio of 0.58.

A typical backlight unit may be made up of one or more (i.e., multiple) L EDs. L EDs may be top view type packages, such as 1616, 2835, 3030, 3535, 3020, 5030, 7020 or other reasonable packages where a relatively large emitting surface area is required, such as for televisions or stand-alone computer monitors.

In addition to the above uses, the phosphors of the present invention can also be used to create saturated colors L ED. the very narrow FWHM of these phosphor materials is comparable to the typical P L emission of direct emission L ED, but is configured to utilize a more efficient blue L ED pump source, for example, the now very good direct emission green L ED has an external efficiency of about 20%, in contrast, the best blue L ED can operate at an external efficiency above 80%, while the normal blue L ED can operate at an external efficiency of about 55% (and can be used to create white L ED at about 145 lm/W), considering the higher radiant luminous efficiency of green (L), even at low external efficiency of 20%, the improvement of direct emission green (L ED) can still far exceed 100lm/W, move from blue (about 26 lm/wrd) to green (>600 lm/wrd), even with low external efficiency, the improvement of direct emission green (L ED) can still be made to be made with a narrow FWHM L, while the FWHM filter can be made to display a wider directly using a CD L, which can still make the white emission leds at a wider spectral efficiency of the CD 38, which can be made to display a direct emission spectrum of green.

The coating may be deposited by a sol-gel process, such as stirring the phosphor powder in a solution of a suitable precursor (such as tetraethoxysilane) in a solvent (such as ethanol), and slowly adjusting the pH of the solution to alkaline, for example using 5M NH₄OH (aqueous), stirred for a period of time, optionally heated, and then the suspension is filtered or decanted to recover the solids. Alternatively, the phosphor can be coated by chemical vapor deposition in a fluidized bed reactor and with an appropriate precursor (such as trimethylaluminum, tetramethoxysilane, tetraethoxysilane, or tetraisopropyl)Titanium alkoxide) and water or ozone to form a metal oxide coating. The phosphor can also be coated by atomic layer deposition, for example, by treating the powder bed with water vapor or ozone to form a hydroxide/oxide layer on the surface of the phosphor, then treating with a metal precursor (such as trimethylaluminum, an alkoxysilane, a titanium metal alkoxide or a chlorosilane or titanium tetrachloride, or other reasonable metal source) to form a metal layer bonded to the oxide layer, then performing another treatment with water to form an oxide-containing layer on top of the metal layer, and then repeating the treatment on the metal precursor until a sufficient number of layers, sometimes as few as 10, and sometimes as many as 200, have been deposited.

Optionally, after coating, the resulting phosphor may be annealed in air, or optionally annealed at a temperature between 200 and 600 degrees celsius in an inert atmosphere, or the phosphor may be additionally coated multiple times. It may also be advantageous to pre-coat the phosphor particles with a buffer layer prior to depositing the transparent metal oxide layer. The formed component of the process is Eu_wCa_1-w(Al_1-zGa_z)_xS_yPhosphor particles (as described above) having an optional transparent buffer layer, and a transparent metal oxide coating comprising silica or alumina. The silica coating may have a percentage of hydroxide and may also have a percentage of aluminum, titanium, yttrium, gallium, magnesium, zinc or other metals that form transparent oxides. The alumina coating may have a percentage of hydroxide and may also have a percentage of silicon, titanium, yttrium, gallium, magnesium, zinc or other metals that form transparent oxides.

Table 1 CIE x, y gamut coordinates for the red, green and blue gamut vertices.

Table 2 green phosphor and resulting color gamut area.

TABLE 3 characteristics of peak position of phosphor (wavelength (nm))

The emission spectrum minimum between the green peak and the red peak is slightly greater than the expected half height of the red peak; instead, the spectral minimum position is used.

TABLE 4 phosphor Peak position characteristics (energy (eV))

The emission spectrum minimum between the green peak and the red peak is slightly greater than the expected half height of the red peak; instead, the spectral minimum position is used.

The present disclosure is to be considered as illustrative and not restrictive. Further modifications will be apparent to persons skilled in the art in view of this disclosure, and are intended to fall within the scope of the appended claims.

Claims (15)

1. A light emitting device comprising:

a light emitting solid state device emitting blue or violet light;

a first phosphor that absorbs blue or violet light emitted by the light emitting solid state device and in response emits green light in a spectral band having a wavelength λ_GPeak value and wavelength lambda of_{G half}The height of the peak half of the spectral band at the long wavelength edge of the band;

and

a second phosphor that absorbs blue or violet light emitted by the light-emitting solid-state device and emits red light in response in a spectral band having a wavelength λ_RPeak value and wavelength lambda of_{R half}The height of the peak half of the spectral band on the short wavelength edge of the band;

wherein, the ratio (λ)_{R half}-λ_{G half})/(λ_R-λ_G) Greater than 0.70.

2. A light emitting device as claimed in claim 1, characterized in that the ratio (λ)_{R half}-λ_{G half})/(λ_R-λ_G) Greater than or equal to 0.75.

3. A light emitting device as claimed in claim 1, characterized in that the ratio (λ)_{R half}-λ_{G half})/(λ_R-λ_G) Greater than or equal to 0.80.

4. The light emitting device according to any one of claims 1-3, wherein the peak of the green spectral band has a full width at half maximum of less than or equal to45 nanometers.

5. The light emitting apparatus according to any one of claims 1 to4, wherein:

the green phosphor is or includes Ca_1-wEu_w(Al_1-zGa_z)._xS_y(ii) a And is

X is more than or equal to 2 and less than or equal to4, y is more than or equal to4 and less than or equal to 7, z is more than or equal to 0 and less than or equal to 1, and w is more than 0 and less than or equal to 1.

6. A light-emitting device according to any one of claims 1 to 5, wherein the red phosphor is or comprises a potassium fluorosilicate based phosphor.

7. The light emitting device according to any one of claims 1-6, wherein the light emitting solid state device emits blue light.

8. The light emitting apparatus of any one of claims 1-7, wherein the combined emission from the light emitting solid state apparatus, the green phosphor, and the red phosphor has a color point on the CIE 1931 chromaticity diagram below the Planckian locus.

9. The light-emitting device according to any one of claims 1 to 8, wherein the first phosphor, the second phosphor, or the first phosphor and the second phosphor are provided on the light-emitting solid-state device.

10. The light emitting device of any one of claims 1-8, wherein the first lumiphor, the second lumiphor, or the first lumiphor and the second lumiphor are spaced apart from the light emitting solid state device.

11. A light emitting device as claimed in any one of claims 1 to 10 wherein the light emitting solid state device is or comprises a light emitting diode.

12. A light emitting device according to any one of claims 1-10, wherein the light emitting solid state device is or comprises a laser diode.

13. A light emitting device comprising:

a light emitting solid state device emitting blue light; and

Ca_1-wEu_w(Al_1-zGa_z)_xS_ya phosphor that absorbs blue light emitted by the light emitting solid state device and emits green light in response;

wherein x is more than or equal to 2 and less than or equal to4, y is more than or equal to4 and less than or equal to 7, z is more than or equal to 0 and less than or equal to 1, and w is more than 0 and less than or equal to 1.

14. The light emitting apparatus of claim 13, wherein the phosphor emits green light in a spectral band having a peak at a wavelength of 500 nm to 545 nm and a full width at half maximum of 25nm to45 nm.

15. The light emitting apparatus of claim 13, wherein the phosphor emits green light in a spectral band having a peak at a wavelength of 535 to 545 nanometers and a full width at half maximum of 25 to 50 nanometers.

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